As a glass plate for automobiles, a colored glass plate (e.g. a heat-absorbing glass plate or a UV-absorbing glass plate) is known, which contains a colorant component whereby transmitted light has a green or blue color tone.
For such a colored glass plate, the solar transmittance is required to be low (e.g. the value, as calculated in a thickness of 4 mm, of solar transmittance (hereinafter referred to also as Te) stipulated in JIS R3106 (1998) is required to be at most 55%). Further, the visible light transmittance is required to be high (e.g. the value, as calculated in a thickness of 4 mm, of visible light transmittance (illuminant A, 2 degrees field of vision) (hereinafter referred to also as Tv) stipulated in JIS R3106 (1998) is required to be at least 70%). Further, the UV-transmittance is required to be low (e.g. the value, as calculated in a thickness of 4 mm, of UV-transmittance (hereinafter referred to also as Tuv) stipulated in ISO-9050 is required to be at most 12%).
Further, as such a colored glass plate, a glass plate tends to be preferred such that when a passenger watches the scenery through the glass plate, the color tone of the transmitted light has a green color tone being a more natural color tone (e.g. the dominant wavelength (hereinafter referred to as also as Dw) of transmitted light stipulated in JIS Z8701 (1982) is from 540 to 570 nm).
Further, for such a colored glass plate, it is desired that types of colorant components be reduced as far as possible and that unit prices of raw materials for colorant components be low, from the viewpoint of costs and with a view to preventing inclusion of impurities at the time of changing the base material (i.e. changing the product type) in the melting furnace to be used for the production of glass.
As colored glass plates whereby transmitted light has a green color tone, for example, the following (1) to (3) have been proposed.
(1) Green glass comprising, per 100 parts by mass of a soda lime silica glass matrix composition,
total iron calculated as Fe2O3: from 0.5 to 2.0 parts by mass,
total titanium calculated as TiO2: more than 1.0 part by mass and at most 3.0 parts by mass,
CoO: from 0.003 to 0.02 part by mass,
Se: from 0 to 0.0008 part by mass,
total chromium calculated as Cr2O3: from 0 to 0.05 part by mass,
total vanadium calculated as V2O5: from 0 to 0.5 part by mass, and
total cerium calculated as CeO2: from 0 to 0.5 part by mass,
wherein the mass proportion of bivalent iron calculated as Fe2O3 in the total iron calculated as Fe2O3 is from 31 to 50%.
(2) UV-absorbing green glass made substantially of soda lime silica glass and comprising, as represented by mass percentage based on oxides,
total iron calculated as Fe2O3: from 0.45 to 0.491%,
total cerium calculated as CeO2: from 1.09 to 1.2%,
total titanium calculated as TiO2: from 0.3 to 0.39%, and
CoO: from 0 to 0.0003%,
wherein the mass proportion of bivalent iron calculated as Fe2O3 in the total iron calculated as Fe2O3 is from 30.5 to 32.0%.
(3) UV-absorbing green glass made substantially of soda lime silica glass and comprising, as represented by mass percentage based on oxides,
total iron calculated as Fe2O3: from 0.52 to 0.63%,
total cerium calculated as CeO2: from 0.9 to 2%,
total titanium calculated as TiO2: from 0.2 to 0.6%, and
CoO: from 0 to 0.002%,
wherein the mass proportion of bivalent iron calculated as Fe2O3 in the total iron calculated as Fe2O3 is from 31 to 38%.
However, the green glass of (1) has a problem such that since the content of CoO is large, Tv is low, and Dw is also low (i.e. transmitted light is bluish green). On the other hand, in the case of the UV-absorbing green glasses of (2) and (3), the content of CoO is small, and the content of total cerium calculated as CeO2 is large, whereby Tv is high, and Tuv is sufficiently low.
However, recently, the prices for cerium raw materials have gone up, and accordingly the cost for green glass having a large content of total cerium calculated as CeO2 has gone up. Therefore, a colored glass plate is desired which contains substantially no cerium and which simultaneously satisfies low solar transmittance, high visible light transmittance and low UV transmittance, while transmitted light has a green color tone.